Apparatus for electrolytic machining



Nov. 15, 1966 K. R. BLAKE 3,285,343

APPARATUS FOR ELECTROLYTIC MACHINING Filed Aug. 15,1962 2 Sheets-Sheet l INVENTOR.

E jam Nov. 15,; 1966 K. R. BLAKE 3,285,843

APPARATUS FOR ELECTROLYTIC MACHINING Filed Aug. 15, 1962 2 Sheets-Sheet 2 INVENTOR. A 7Z776;/ F3

United States Patent 3,285,843 APPARATUS FOR ELECTROLYTIC MACHINING Kenneth R. Blake, Huntington, lnd., assignor, by mesne assignments, to Micromatic Hone Corporation, Detroit, Mich., a corporation of Michigan Filed Aug. 15, 1962, Ser. No. 217,084 1 Claim. (Cl. 204224) This invention relates to electrolytic grinding and method, and particularly to electrolytic grinding employing a shoe electrolytically associated with the work.

For quite some time electrolytic grinding has been employed for increasing the speed of metal removal from hard materials which resist normal grinding. In this arrangement, the workpiece was connected to the positive side of a current delivering device to form an anode, while the negative surface was connected to a conductive grinding wheel which functioned as the cathode. The abrasive element of the wheel will remove the roughened material from the workpiece by the plating effect by the current passing through the workpiece to the electrolyte and wheel. 1

The present invention pertains to the use of a conducting shoe having a face disposed adjacent to the surface of the workpiece, being spaced therefrom by insulating elements distributed about the face and having a negative conductor connected thereto to produce a deplating action between the workpiece and the electrolyte flowing between the conductive surface of the shoe and the workpiece. The shoe may be hollow having apertures extending through the face so that an electrolyte may pass therethrough, or the electrolyte may be directed from a nozzle between the shoe and the surface of the workpiece. A substantially heavy current can be employed through the workpiece and shoe to substantially increase the deplating operation.

The shoe may be formed to mate with the contour of any workpiece, such as an inner raceway, for example, the face of the shoe being concave in one direction and convex in the other direction to follow the toroidal recess of the raceway. The shoe would having insulating projections so as to be spaced from the raceway and be disposed opposite to a formed grinding wheel which grinds the toroidal surface in the presence of the current and the electrolyte which will substantially reduce the time required for grinding the hard materials of the surface. The use of the shoe and higher currents alone or in combination with the electrolytic grinding wheel reduces the time of metal removal many fold and the cost of the machining operation.

Accordingly, the main objects of the invention are: to provide a conducting shoe having a face which mates with the surface of the workpiece to be ground, having insulating particles thereon for spacing the shoe face a predetermined distance from the surface of the workpiece; to pass a heavy current through the workpiece and an electrolyte to a spaced shoe on one side thereof while current is passed to a conducting wheel which engages the surface of a workpiece at a point opposite to the point engaged by the nonconductive particles of the shoe; to provide a conductive shoe having a face matable with a surface to be finished and having a hollow interior from which a plurality of apertures extend to the face through which an electrolyte will pass to the surface to be machined which will be deplated by a current passing from the workpiece to the shoe, and, in general, to provide a shoe for substantially increasing the removal of metal from a workpiece which is simple in construction, positive in operation and economical of manufacture.

Other objects and features of novelty of the invention will be specifically pointed out or will become apparent when referring, for a better understanding of the inven- 3,285,843 Patented Nov. 15,, 1966 tion, to the following description taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a view in elevation of a machine having a shoe thereon embodying features of the present invention;

FIG. 2 is an enlarged sectional view of the structure illustrated in FIG. 1, taken on the line 22 thereof;

FIG. 3 is an enlarged, broken view of the structure illustrated in FIG. 2, as viewed within the circle A thereof; FIG. 4 is a broken view of structure illustrating another form of workpiece to which the invention has been applied;

FIG. 5 is a perspective view of structure, similar to that illustrated in FIG. 2, showing another form of the invention;

FIG. 6 is an enlarged sectional view of the structure illustrated in FIG. 5, taken along the line 6-6 thereof, and

FIG. 7 is an enlarged broken view of the structure illustrated in FIG. 6, as viewed within the circle 7 thereof.

Referring to FIGS. 1 to 3, a grinding machine 10 is illustrated having a headstock 11 and a tailstock 12 for supporting a workpiece 13 which is rotated by the driving mechanism 14 of the headstock. A table 15 advances a grinding wheel 16 and a conducting shoe 17 along the workpiece 13 for performing a Work operation thereon.

As illustrated more specifically in FIG. 2, the shoe 17 is made of copper or.other conductive material having insulating particles 18 in the face 19 thereof which space the face a predetermined distance from the surface of i the workpiece 13. A link 21 is pivoted to a boss 22 on the outer face of the shoe and to a support 23 so as to be movable toward and away from the workpiece. A spring 24 is secured to a link 21 and to a support 25 by a screw 26 by which the tension of the spring may be adjusted. A terminal 27 is secured to the shoe 17 by a nut 28 on a stud 29.

A tube 31 delivers a coolant between the workpiece 13 and the grinding wheel 16, and a tube 32 delivers an electrolyte to the surface of the workpiece and that of the shoe 17. In FIG. 2 the tube 32 is illustrated as being a branch of the tube 31 so that the electrolyte functions as a coolant when delivered to the workpiece at the wheel.

A shunt 33 on the shoe is connected to a conductor 34 leading from a negative source of current and a conductor 35 from a positive source of current is. connected to the workpiece 13. Up to 300 amps of current may be passed between the workpiece 13, the electrolyte and the shoe 17 to produce a deplating operation, that is to say, for removing material from the surface of the workpiece which is picked up by the electrolyte and carried therefrom. This deplating operation roughens or pits the surface of the workpiece to have the surface more susceptible to the attack by the abrasive elements of the grinding wheel which are maintained in sharp condition by the roughened surface. Extremely fast removal of the material occurs by the depl'ating operation and by the more rapid cutting of the material by the grinding wheel. The deplating and abrading operations occur in areas located in an annular surface area which is coaxial with the workpiece so that one operation follows the other.

When the wheel 16 is made of a conducting material, a conductor 36 from a negative source may be connected thereto so that deplating of the material of the workpiece surface will occur at the line of junction between the workpiece and the grinding wheel. In view of the line contact engagement, less current will pass between the wheel and workpiece and less deplating will occur thereat while a greater amount of deplating will occur at the greater area of current flow between the shoe and the workpiece surface.

In the conventional grinding of a standard .5 x .5 tool steel bit having a .25 area employing a 60-1-8 aluminum oxide wheel and oil as a coolant, a comparison test was made. The test specimen was of tool steel known in the trade as Neatro 66 Rockwell C having a specific gravity of 8.16. The removal of .001 inch in one minute equaled .00025 cubic inch per minute with a showing of burning to the surface. When using a similar test piece and process employing 150 amperes between the wheel and test specimen, the removal rate was .0052 cubic inch per minute which provided a ratio of 20 to 1 of the electrolytic process over the standard process with no apparent burning to the surface.

In FIG. 3, a further form of the invention is illustrated that wherein an inner raceway 40 of a ball bearing is being machined by the herein described process. A shoe 41 has an arcuate convex face 42 with insulating projections thereon to mate with the transverse curvature of the raceway and a concave face to nest with the toroidal surface of the raceway. Opposite to the shoe 41 a grinding wheel 43 has a formed surface 44 which mates with the raceway when ground to form. A current is passed between the workpiece and the shoe to perform the deplating operation while the grinding wheel performs the grinding operation on the roughened surface produced by the deplating operation. It is to be understood that when the grinding wheel 43 is of conductive material current can be passed between the workpiece and the wheel in the same manner as described with regard to the structure of FIGURE 2.

Referring to FIGURES 5, 6 and 7, a further form of the invention is illustrated, that wherein a shoe 45 is supported on links 21 and tensioned by a spring 24 against the surface of a workpiece 13. The shoe 45 has a body 46 of copper or similar conductive material to which a cap 47 is sealed to form a reservoir to which an electrolyte is delivered by the conduit 48. The body 46 has a plurality of apertures 49 therethrough from which the electrolyte in the reservoir is delivered to the surface of the workpiece 13. The body 46 remains spaced from the surface by the plurality of insulating projections 18. A U-shaped conducting bar 51 is secured at opposite sides of the body 46 by screws 52. A terminal 53 on a conducting bar 51 has a conductor 54 secured thereto by a nut 55. Current will readily pass through the conductor 54, the U-shaped conducting bar 51 to the conducting body 46. The electrolyte from the conduit 48 is fed between the faces of the workpiece 13 and the conducting body 46 which are spaced by the particles 18. The body, being located opposite to the grinding wheel 16, will deplate and roughen the surface of the workpiece so that the grinding wheel is more effective for the removal of material, whether of the conductive or nonconductive type. If of the former, current may also be passed thereto from the workpiece through an electrolyte passing therebetween.

What is claimed is:

In a machining device for a workpiece, means for rotating a workpiece, a conducting shoe having a face substantially matable with the face of the workpiece, insulating means on the face of the shoe spacing said shoe from the workpiece surface, conducting means for passing a flow of current from said workpiece to said shoe, means for delivering an electrolyte between the shoe face and adjacent workpiece surface, means for abrading said workpiece surface, said abrading means having a conducting body, means for conducting current from the workpiece to said abrading means, and means for delivering an electrolyte to said abrading means at the point of engagement with the workpiece, said shoe performing a deplating operation in an area spaced from the area in which the abrading operation occurs, said area being deplated and said area being abraded being located in an annular surface area which is coaxial with said workpiece axis so that the operation in one area follows that in the other area.

References Cited by the Examiner UNITED STATES PATENTS Keeleric: Steel, vol. 130, No. 3, pp. 84-86, March 17, 1952.

JOHN H. MACK, Primary Examiner. R. L. GOOCH, R. MIHALEK, Assistant Examiners. 

